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  • "R1/4" thread. What is it?

    Discussion in 'Machining' started by GarethW, May 26, 2011.

    1. GarethW

      GarethW Chief Clicker Staff Member

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      I need to fit this part (pictured below) to something. It has a "R1/4" thread. Anyone know what that means? Is it an ordinary 1/4" BSP thread or is it some kind of fancy thread with non-parallel sides?

      [​IMG].
       
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    3. PWASS

      PWASS Well-Known Member

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      Gareth

      The 'G' and 'R' thread designations were added when BSP threads were adopted by the metric system for pipe threads.

      'G' is the same as BSPP (parallel thread), 'R' is the same as BSPT (tapered thread).
       
    4. GarethW

      GarethW Chief Clicker Staff Member

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      Thanks for the help. I had some samples come through today in the post. The overall diameter of the thread measures more like 1/2", so I'm pretty confused about the "1/4" designation. I made some measurements in metric: the diameter of the thread is 12.9mm at the top, tapering up to 13.3mm at the base. The length of the threaded part is 11mm. I'll drop the samples off to a machinist on Tuesday. Hopefully he can cut the right type of female thread for me.
       
    5. PWASS

      PWASS Well-Known Member

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      Gareth

      BSP Pipe threads are sized according to the thread that can be machined onto that size bore pipe, so a 1/4" BSP thread measures 0.518" or 13.15mm

      Tapered threads are used when a shoulder is not available to seal against like threading the OD of a pipe and should be screwed into a female tapered thread.

      Tapered threads are prone to leakage but have the benefit of being positional.
       
    6. Oleg

      Oleg New Member

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      Look at this...
      [​IMG]
      or this
      [​IMG]
       

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